3500 swap questions

[PCGUY112887]

Well I was looking at the headers and it looks like they put the bung for the O2 right in the crossover area (far away enough from the ports for the wideband). I have also read a few posts that say the headers need no modification, and 1 that said that the flange had to be modified a bit or it would bump against the firewall.

So I just ordered the headers

Damn you Isaac... making me spend money

Anyone have any idea how long they take to ship? I have been calling them all day and I sent them an email this morning but I haven't been able to get ahold of anyone.

[Superdave]

S&S is usually pretty quick although they "forgot" to ship me an order a while back.. i called after a month of waiting and they overnighted it to me.

[IsaacHayes]

Hahha yes I know it costs more but it's a project car might as well do it right and get some more power from headers! You want it to be fast right?

I think you'll have to cut off the flange and position it different or put your own flange on or something would be my guess... But modifying the downpipe isn't that hard to get it to fit compared to what it would take in an L body.

The O2 bung is in the cross over yes. Not the most ideal spot, so it would be best to weld in a nut in the down pipe somewhere for the O2 sensor(s) so they can read both banks. You can cap the cross over bung with a bolt of the right size then.

[PCGUY112887]

So should I use my 3500 exhaust gaskets, or ones from a 3400, or does it really matter with these headers?

My friend has a camaro and he was reading into headers. He has to get special grade 8 bolts, lock washers, loctite, etc etc etc to keep the bolts for his headers in. Everyone seems to have problems with the bolts backing out and the headers leaking like mad. Am I going to have issues like this, or will just using the stock bolts/studs be just fine?

[Superdave]

i'm using the stock studs (the 8 that stayed in) with the original nuts.. the rest are held in by 3400 oil pan bolts. No loctite and they're staying tight.


you'd use the 3400 gaskets with those headers.

[Joseph Upson]

So should I use my 3500 exhaust gaskets, or ones from a 3400, or does it really matter with these headers?

My friend has a camaro and he was reading into headers. He has to get special grade 8 bolts, lock washers, loctite, etc etc etc to keep the bolts for his headers in. Everyone seems to have problems with the bolts backing out and the headers leaking like mad. Am I going to have issues like this, or will just using the stock bolts/studs be just fine?

I believe it's just a camaro thing, the headers on mine were a problem also. The significant difference here is that the rear wheel drive engines don't typically use studs and nuts as stock equipment and those found on the fwd cars use lock nuts so it's unlikely that you'll have a problem.

[PCGUY112887]

A few of my exhaust studs came out... just stick em back in and torque em tight? I've never used studs before... didn't know if there was anything "special" to them or not.

Does anyone know if the 3500 torque specs are any different than the ones printed in my GM book for my 3100?

[Superdave]

^ they shouldn't be but the 3500 torque specs are on this site


the bolts i used on my iron heads in the Trans Am did back out, i just got the engine warm and tightened them down once or twice.. they've never come loose since.

Iron heads suck

[PCGUY112887]

Thanks, I got the specs printed off.

If I pull the heads off, am I going to need new head bolts? Since I have new headgaskets with this GM kit, it almost seems easier to just pull the heads off to change the springs vs trying to feed a rope into each cylinder or something to keep the valves from falling out.

[Superdave]

Yep, new headbolts are cheap.

all the aluminium head OHV '660's use the same ones so if they say they don't have them for your engine then ask for a set for a '99 GAGT-3400.

[PCGUY112887]

The ones for my 3100 are different than the ones for the 3400 (different part #'s) and they don't have any listed for the 3500.

The picture shows half of the bolts being longer than the other half for the 3400, and they are all the same for the 3100.

[SappySE107]

They are not all the same length on the 3100. They are the same heads so they are also the same head bolts.

[PCGUY112887]

So I'll be fine with ones from a 3400?

[Superdave]

So I'll be fine with ones from a 3400?

That's what i'm using...


the 3400/3500 ones were the same as the ones i pulled from my old 2.8 (just cleaner). I have a bucket full of used headbolts from these engines.

[PCGUY112887]

What plugs are you using Superdave? Should I go with some colder ones, or use the stock ones?

The stock iridium ones are in there right now, haven't pulled them yet but I bet they are fine.

EDIT - May sound stupid, but how do you do the valvesprings? I know you use the spring compressor and it will compress them down, but then how do they come off?